Heat pump systems



J. R. HARNISH HEAT PUMP SYSTEMS March 15; 1960 4 Sheets-Sheet 1 FiledApril 4, 1957 IN VEN TOR. 40155 R. HAM/5A! ATTO March 15, 1960 J. R.HARNISH HEAT PUMP SYSTEMS 4 Sheets-Sheet 2 Filed April 4, 1957 an m 4 J3 u a /3 6/ fi t L v 2 M g 4, 2T T 1 m w w u w 2 fi I INVENTOR. v 40155R. HARM/5H Mafch 15, 1960 J. R. HARNISH 2,923,255

' HEAT PUMP SYSTEMS Filed April 4, 1957 4 Sheets-Sheet 3 IN V EN TOR.

JnnzsRJ/amwsu March 15, 1960 J. R. HARNISH 2,928,255

' HEAT PUMP SYSTEMS Filed April 4. 1957 r 4 Sheets-Sheet 4 95%}1 is Mmmvrox. uiwzs R. /7'ARNI5/l HEAT PUMP SYSTEMS James R. Hamish, York,Pa., assignor to Borg=Warner Corporation, Chicago, 111., a corporationof Iiiinois Appiicatian Aprild, 1 957, Serial N o. 650,679

4 claims. or. 6281) This invention relates to heat pumps and moreparticularly to defrosting arrangements therefor. As is well known, aheat pump is a reversed refrigerating apparatus wherein an outdoorheat-exchanger picks up heat from outside air, water or the ground, etc.with this heat sustained cold periods below approximately 30 F. How-.ever, with the continual refinements and improvements in heat pumpsystems, such as shown, for example, in application No..5.1-7,971, nowPatent No. 2,869,335,

owned by the assignee of my invention, their use has now been extendedto colder areas where formerlythey were considered unsuitable for use.

With such a heat pump system utilizing outside air as a heat sourcethere arises the problem of defrosting the outdoor heat-exchangerrefrigerant coil. A temperature diiferential of between and 25 must bemaintained between the outside air and the refrigerant within the coilso that heat may flow from the outside air to the refrigerant. Undercertain conditions of operation, with low temperature and high humidityconditions, a considerable fro-st build-up on the coil will ensue,therebyfcutting down the heat transfer ability of the heat-exchanger.Means must, therefore,be provided for either periodical- 1y defrostingthe coil at some predetermined timed intterval, or for automaticallysensing a frost build-up on the coil and initiatingthe defrostingmechanism when that frost build-up has reached some predetermined point.

On what is known as an air-to-air heat pump wherein frigeratingoperations. It will be appreciated, however,

that there will be a great danger of freezing the water.

within the indoor heat-exchanger since the sub-freezing temperaturestherein will be maintained by the compressor duringthe entire defrostcycle. 7 A typical liquid type indoor heat-exchanger will consis t of aliquid tight shell having a tube bundle mounted therein. This danger offreezing is present even in that typeof heat-exchanger whereinrefrigerant is circulated within the tubes of the heat-exchanger and thewater to be heated or cooled circulates over the tubes since anaccumulation of ice within the shell could be detrimental. The problem,

. however, is considerably more aggravated in that type outside air isthe heat source and theyfluidjtobe heated is room air, this defrostingarrangement can be effected by reversing the apparatus wherein theindoor heat-ex-" changer functions as an evaporator taking heat awayfrom the room air and the outdoor heat-exchanger func tions as acondenser melting any frost accumulated on the coil thereof. Thisprocedure can be followed even though a freeze-up of the indoorheat-exchanger might occur since such a freeze-up would not bedetrimental.

However, in those heat pump systems known as airto-liquid, wherein heatpicked up from outside air is transferred to a liquid such as water, forheating the same, this procedure of reversing the operation of the heatpump is not readily available. With the outdoor coil considerablyfrosted and therefore at a substantially constant temperature no greaterthan 32 F. and at a pressure substantially corresponding thereto,reversing the operation of the heat pump must, of necessity, lower thepressure within the indoor heat-exchanger to'a value where its pressureand corresponding temperature will be lower than that of the outdoorcoil as in normal reof heat-exchanger wherein the water circulateswithin the tubes and the refrigerant flows thereover. It can be readilyseen that the freezing of the water within the tubes could result inrupturing the tubes with a consequent break-down of the system,

in Patent No. 2,430,938, assigned to the assignee of my invention, thereis disclosed a defrosting arrangement admirably suited for heat pumpoperation. As shown therein, when defrosting of the outdoorheat-exchanger (evaporator) is necessary, the compressor is stopped andthe outdoor heat-exchanger and indoor heatexchanger (condenser) areplaced in free communication so thatthe pressures therebetween mayequalize. Liquid refrigerant within the outdoor heat-exchanger thenflows by gravity to the'indoor heat-exchanger picking up heat from aheat-exchange liquid flowing therethrough and becoming vaporizedthereby. The vapor builds up in pressure within the indoor.heat-exchange r to apoint where it will fiow to the outdoor,heat-exchanger 'giving up its heat therein for defrosting purposes. Ingiving up itsheat, the refrigerant vapor is condensed thereby completingthe cycle. I V

In such an arrangemenL-th'e pressure andtemperature in theindoorheat-exchanger remains at a substantially elevated level during thedefrosting cycie minimizing the danger of ice formation therein. I

' The disclosed defrosting method, however, is not completely suitablefor my purposes in that the operation is not automatic. While manualoperation'is feasible, it will be apparent that automatic operation isfar more desirable and, in fact, necessary in large installations. Inaddition thereto in the disclosed defrosting method, oncethe defrostingis accomplished, and the system put back into normal operation, it takesa relativelyulong "-period of time for the liquid refrigerant within thein- It is an ob ect or the mventzon, therefore, ,to provide a defrostingarrangement for a heat pump including a compressor, anair-to-refrigerant outdoor heat-exchanger and a refrigerant-to-liquidindoor heat-exchanger wherein the compressor is shut 'down'andunevaporated refrigerantis allowed to "flow'from the outdoor to theindoor heat exchanger to absorb heat from the fiuid therein, andevaporated refrigerant flows from the indoor to the outdoorheat-exchanger giving up its heat for defrosting the outdoorheat-exchanger, and means are provided for rendering the entireoperation automatic. Another object of the invention is to provide adefrosting arrangement of the type above-mentioned wherein means areprovided for quickly returning liquid refrigerant from the indoorheat-exchanger to'the outdoor heat-exchanger after the termination ofthe defrosting operation.

Yet another object of the invention is to provide a heat pump comprisinga compressor, an indoor heat-exchanger and an outdoor heat-exchanger andmeans for defrosting the heat pump, the defrosting means comprisiiigmeans for deactuating the compressor, and means for equalizing thepressure between the two heat-exchangers for liquid refrigerant to flowby gravity from the outdoor to the indoor heat-exchanger absorbing heattherein and becoming evaporated, with the evaporated refrigerant thenflowing to the outdoor heat-exchanger between the indoor and outdoorheat-exchanger, allowing the pressure to equalize therein; liquidrefrigerant within the outdoor heat-exchanger then flows by gravitythrough one of the flow paths to the indoor heat-exchanger picking upheat from the heat-exchange liquid therein and becoming vaporized; thisvapor builds up in pressure sufliciently to flow through the other ofthe flow paths back to the outdoor heat-exchanger where it gives up itsheat for defrosting the outdoor heat-exchanger and becomes condensed tocomplete the cycle, all as is shown in the aforesaid Patent No.2,430,938. In addition, means are provided for rendering the entireoperation automatic.

n terminating the defrost cycle, I provide means for first closing theflow path for the refrigerant vapor. In so doing, the pressure in theindoor heat-exchanger builds up to a point corresponding to itstemperature, which, of course, is considerably higher than that of theoutdoor heat-exchanger. By virtue of this difference in pressures, theliquid in the indoor heat-exchanger is then forced through the stillopen liquid flow path back to the outdoor heat-exchanger, at which timethe normal heating cycle again commences, with refrigerant flow betweenthe two heat-exchangers being at a controlled rate.

The invention consists of the novel constructions, arrangements anddevices to be hereinafter described and claimed for carrying out theabove-stated objects and such other objects as will appear from thefollowing description of preferred embodiments of the inventiondescribed with reference to the accompanying drawings, in which:

Fig. 1 is a schematic representation of a heat pump embodying the noveldefrosting arrangement and includes electrical controls;

Fig. 2 shows refrigerant flow paths on the cooling cycle;

Fig. 3 shows refrigerant flow paths on the defrost cycle;

Fig. 4 shows an alternate control means for initiating the defrostcycle; and

Fig. 5 shows a heat-exchange liquid circuit for a system utilizing morethan one heat pump.

Turning now to the drawings, the basic components of the heat pumpcomprise a compressor driven by an electric motor 11, an indoorheat-exchanger 12 and an outdoor heat-exchanger 13.

Indoor heat-exchanger i2 is preferably of a shell and tube typeincluding, a tube bundle 14 therein through which the heat-exchangeliquid to be either heated or cooled is circulated. Heat-exchanger 12may be located anywhere within the building to be conditioned.

The heat-exchange liquid circuit comprises essentially a plurality ofheat-exchangers 15 located in the spaces to be conditioned and connectedto tube bundle 14 by way of liquid lines 16. A pump 17 has its inletconnected to the heat-exchangers 15 by liquid lines 28 and its outletconnected to tube bundle 1d of indoor heat-exchanger 12 by way of aliquid line 19.

Heat-exchanger 13 is located generally on the roof of the building, orin any other area in free communication with outside air. Heat-exchanger13 must be a suflicient height above heat-exchanger 12 so thatrefrigerant liquid will flow by gravity from the outdoor heat-exchangerto the indoor heat-exchanger when defrosting is desired. Heat-exchanger13 comprises a casing 2% having therein a refrigerant coil 21 throughwhich is circulated the refrigerant to be either evaporated orcondensed, depending on whether the system is heating or cooling.Outside air is circulated over the coil by a fan 22, of any suitabletype, located Within the casing or adjacent thereto and driven by anelectric motor 23. An air inlet opening 24 is provided in casing 24! forallowing air to be drawn over the coil 21, the air then being dischargedthrough an outlet opening 25 provided for this purpose. A drip pan 26provided with an outlet line 27 is provided for receiving the drip offof coil 21 and draining it away to the sewer. It will be appreciatedthat a forced draft system could instead be utilized wherein the fanwould be located on the air entering side of the heat-exchanger.

When referring to an indoor heat-exchanger, I mean only that theheat-exchanger is in heat-exchange relation with the liquid to be heatedor cooled, which liquid is then utilized in heat-exchangers 15 forheating or cooling the space to be conditioned. When referring to anoutdoor heat-exchanger, I mean only that this heat exchanger is inheat-exchange relation with outside air for dissipating heat when thesystem is cooling, or picking up heat when the system is heating. Itwill be appreciated, then, that the terms indoor and outdoor refer tofunction rather than location Suitable refrigerant flow lines areprovided between compressor 10, indoor heat-exchanger 12 and outdoorheat-exchanger 13, including a hot gas refrigerant line 28 and branchlines 29 and 30 connected thereto by way of three-way valve 31. -It willbe appreciated that in one position of valve 31, gas refrigerant line 28will be communicated with branch line 29, while in the other position ofvalve 31, gas refrigerant line 28 will be cornmunicated with branch line30. A suction line 32 having a valve 33 therein joins one end of coil21'with the inlet of the compressor It The other end of coil 21 connectswith the indoor heat-exchanger by way of a liquid line 34 having a valve35 therein. Liquid line 34 also contains a refrigerant feeding .devicesuch as a thermal expansion valve. 36 controlled by a bulb 37 connectedthereto by way of a capillary '38, bulb 37 being in heat-exchangerelation with suction line 32. An increase in temperature in the gasflowing through suction line 32, indicatin that insuificient liquidrefrigerant is being admitted to coil 21,. acts through bulb 37 andcapillary 38 to open thermal expansion valve 36 more fully to admit moreliquid to coil 21. Conversely, on a decrease in temperature in suctionline 32, thermal valve 36 is slightly closed to decrease the amount ofrefrigerant fluid admitted to coil 21. A bypass 39, containing a valve40, is provided for bypassing the thermal expansion valve 36 when thesystem is on the cooling cycle or defrosting cycle. A bypass 41 isprovided around valve 35 and has a refrigerant feeding device such as athermal expansion valve '42 therein, controlled by a bulb 43 connectedthereto by way of capillary 44; bulb 43 being in heat-exchange relationwith branch line 30. A bypass line 45 controlled by a valve 4-5 isprovided for joining branch line 36 with suction line 32.

A pressure responsive control 47 is provided for automaticallyinitiating a defrost cycle upon a predetermined accumulation of frost oncoil 21. The control 47 includes a housing 48, having a diaphragm 49therein, dividing the housing into two chambers 50 and 51. Chamber 50 iscommunicated with the outdoor heat-exchanger adjacent to fan 22 by wayof a line 52 terminating in a restricted orifice 53. Chamber 51 ismaintained at atmospheric pressure by aline 54,.terminating in arestricted orifice 55, line 54 being so arranged that it will at. alltimes be subject to atmospheric pressure.

The system includes an electrical control circuit comprising main lines56 and 57 directly connected to electric motor 11. A solenoid switch 58,including asolenoid 59 and switch arm 60, is provided in line 57 forbreaking the circuit to motor .11 when the defrost cycle is initiated.Fan motor 23 is connected to line 56 by way of a lead 61 and isconnected to line 57 by leads 62 and 63. Lead 62 has a solenoid switch64 therein including, a solenoid 65 and aswitch arm 66. A conventional'time controlled device 67 and a conventional time off delay relay 68with an adjustable time off are provided for regulating the length ofthe defrost cycle. I Time controlled device 67 may be of the type shownin the Paragon Electric Company bulletin No. BTS-lOZ-l, Drawing 'No.C-34C, as an fInterval Timer, Model Z, Type 41, Pilot lA, Reset 1, andincludes a timer 69, controlling a'switch arm 70 for closing a normallyopen switch 71. Time controlled device 67 is of that type whereinanelectrical circuit is set up through timer 69 lead 112.

Solenoid 90 has one side connected to switch 107 by "a lead 115. Theother side of solenoid 90 is directly con- .nected to lead 103.Solenoid'91 is connected across leads 103 and 115 by leads 116 and 117respectively. Soleto close switch 71 for a predetermined time interval,as

determined by the timer 69. After the predetermined time interval, theelectrical circuitthrough the timer 69 is broken thereby, and switch 71assumes its normally open position. Time off delay relay 63 may be ofthe type shown in the Allen-Bradley bulletin No. 849', page .111, styleNoJB, and includes a delayed action timer 72, controlling a switch arm73 for opening'or opening or closing a normally open switch 74. Y Timeoff delay relay 68 is of the type wherein an electrical circuit is-setup through delayed action timer 72 to close switch 74. Delayed actiontimer 72 is not a'self de-energizingitimer as is timer 69, but isinstead of the type wherein,,,upon' de-energization thereof, s'witch74is maintained in its closed position for a set, predetermined timeinterval as determined by timer 72, after which timeit assumes itsnorrnally open position. Timer 69 has one side connected to line 56 byleads 75 and 76 interconnected by a normally open switch 77. Switch 77is adapted to be closed by a switch arm 78 connected to diaphragm 49.The other .side of timer 69 is connected to line; 57 by way of lead 79and the aforementioned lead 63 ,to..complete the circuit through thetimer when switch 77 is closed. Switch.71 has one side thereof connectedto lead 76 by :a lead 80 and the'j'other side thereof is connected to alead 31. Delayed action timer 72. hasone "side thereof connected to lead81 by a lead 82and the other side thereof is connected toline-63 by alead 83. Switch 73 has oneside thereofconnected to lead 76 v by ,a lead'04v and the other side thereof connected to, a lead 85.

Solenoid 65 has-one side thereof connected to lead 85 by. a lead 86. Theother side of solenoid 65 is connected directly tov lead 63. Solenoid 59is connected to lead. 85 by a lead 87 and to linef57 by a lead 88. Aholding circuit for timer 69 is provided through'a lead 89 connected tolead 86. r H H In order to render the operation of valves 31, 33;, 35,40 and 46 ..autornatic, they are provided with'solenoids '90, 91, 92, 93and id-controlling valve cores 95, 96,, 97, 93 and 99 respectively. i i

. Valves 40 and 46, which are normally closed for the heating cycle,must be open for the defrosting cycle, for

reasons to .be later explained; This is provided for as follows: valve40 has one side of solenoid 93 connected to lead 86 by way of a lead 100and the other'side there-- of connected to line 57 by way of a lead 101.Solenoid 94 of valve 46 has one side thereof directly connected to and106.

noid 92 has one side. thereof connected to lead by a lead 118 and theother side is connected to lead 101 by a lead 119. Switch 105 has theother side thereof connected to lead 81 by a lead 120. Switch 106 hastheother side thereof connected to lead 100 by .a lead 121. Current issupplied to lines 56 and 57 through a master witch 122 connected to anysuitable source of supply.

in operation, when cooling is desired, the operator moves sliding arm111 to the right from its position shown in Fig. 1, thereby closing acircuit through switches Master switch 122 is closed, and electricmotors 11 and 23 are energized, thereby operating compressor 10 and fan22. By virtue of switches 105 and 106 being closed, solenoids-941 and 93of valves .46 and 40'are energized, raising valve cores 99 and 98 totheir upper position, thereby allowing flow through the valves, asfollows: on the closing of switch .105, a circuit is completed to oneside of; solenoid 94-frorn line 56 by wayof lead 112, lead 113,.switch105, lead and lead .81. ,The other side of solenoid94 is connected toline On the closing of switch 106, a circuit is completed to 'one sideof solenoid 93 from line 56 by way of lead 112, switch 106, lead 121 andlead 100. The other side of solenoid 93 is connected to line 57 by lead101, thus completing'the circuit.

With sliding arm111 in its cooling position, switch107 is open. Withswitch 107 open, the circuit to solenoids 90, 9'1 and 92is broken andvalve cores 95, 96 and 97 respectively are in their lower orde-energized position. Valve 31 then communicates lines 2S and 29 andvalves 33 and 3,5 are closed.

As shown particularly in Fig. 2, cornoressed refrigerant gas then flowsfrom the compressor 10 through line 28 and valve 31 into line 29 fromwhence it flows part way through line 32 into coil 21 where it gives upits heat and is condensed by the air flowing thereover under the,influence of fan 22. Suitable means (not shown) may also be provided forsor ayingwater over coil 21. The liquid refrigerant then flowsthroughbyp ass line 39, open valve .40, into line 34. With valve 35closed, the liquid fiows intolinel and through thermal valve 42, wherebyits pressure and corresponding temperature is reduced. The

cold liquid refrigerant then fiowsinto heat-exchanger 12 g and removesheat from the-heat-exchange liquid (generally water) flowing through,tube bundle 14, thereby chilling the liquid. in removing this heat, therefrigerant becomes evaporated with the refrigerant gas leaving theindoor heat-exchanger by way of line 30. With valve 46 open, the gaseousrefrigerant flows through bypass 45 into line 32 and thence back tocompressor v1.0 to complete the circuit.

When heating isdesired, the o erator moves sliding arm 111 to the leftto the position shown in Fig. 1. With sliding arm 111 in its heatingposition, switches 105 and 1% are open as shown, and switch 107 isclosed. The opening of switches 105' and 106 breaks the circuits tosolenoids 94 and 93 respectively, allowing the valve cores 99 and 90 todrop to their lower or deenergized position, closing valves 46 and 40.

The closing of switch 107 energizessolenoids 90, 91 and 92 as follows:on the closing of switch 107, a circuit is completed to one side ofsolenoid 90 from line 56 by lead 112, lead 114, closed switch 107 andlead115. The

other side of solenoid 90 is connected to line 57 by lead seesaw 103 andlead 101. Since solenoid 91 is directly connected across leads 103 and115, it also is energized on the closing of switch 107. Solenoid 92 isalso energized on the closing of switch 107, since it is directlyconnected across lines 191 and 115.

Energization of solenoids 96, 91 and 92 actuates valve cores 95, 96 and97 respectively to their upper position. This has the effect of openingvalves 33 and 35. Insofar as valve 31 is concerned, with valve core 95in its upper position, this communicates hot gas refrigerant line 23with branch line 3%).

Hot compressed refrigerant gas then exits compressor by way of line 28and is directed by valve 31 into line 39, whence it flows into theindoor heat-exchanger 12, giving up its heat to the water orheat-exchange fluid flowing within the tube bundle 14 and becomingcondensed thereby. Liquid refrigerant then exits heat-exchanger 12 byway of line 34 and flows through open valve 35. Since valve 49 isclosed, the refrigerant fluid flows through thermal valve 36 where itspressure and corresponding temperature are reduced and then into coil 21where it picks up heat from air flowing thereover under the influence offan 22, becoming vaporized thereby. Refrigerant vapor exits coil 21. byway of line 32 through now open valve 33 and back to the inlet ofcompressor 1 to complete the heating cycle.

Upon a build up of frost on coil 21 sufficient to impede the flow of airthrough inlet opening 24 and over the coil, fan 22 pulls a partialvacuum within heat-exchanger casing 20. The less than atmosphericpressure existing within casing 20is communicated to chamber '59 by line52. Since chamber 51 is always at atmospheric pressure, as pointed outabove, diaphragm 49 is forced to the left and switch arm 78 closesnormally open switch 77. Upon the closing of switch 77, timer 69 isenergized as follows: current flows from line 56 through lead 76, closedswitch 77 and lead 75 to one side of the timer and thence through leads79 and 63 back to line 57. On energization of timer 69, switch arm 70 isactuated to its upper position closing switch 71. Timer 69 thenmaintains switch arm 70 in its upper position for the set time interval.

With switch 71 closed, a circuit is completed through delayed actiontimer 72 as follows: current flows from line 56 through lead 76, lead80, closed switch 71, leads 81 and 82 to one side of timer 72 and thencethrough leads 33 and 63 and back to line 57. On the energization oftimer 72, switch arm 73 is actuated to its upper position, closingswitch 74. As was pointed out above, delayed action timer 72 is sodesigned that it holds switch arm 73 in its upper position for a settime interval after the timer is die-energized. The closing of switch 74also has the effect of breaking the circuit to compressor motor '11,stopping the operation of compressor 19 as follows: solenoid 59 isenergized by current flowing from line 56 through lead 76, lead 84,closed switch 74, lead 85, lead 87, through solenoid 59 and lead 88 backto line 57. Energizing solenoid S9 actuates switch arm 6% to its upperposition, breaking the circuit to motor 11, as aforementioned.

With switch 74 closed, solenoid 65 is energized to actuate switch arm 66to its upper position as follows: current flows from line 56 throughlead 76, lead 84, closed switch 74, lead 85, lead $6, thence throughsolenoid coil 65 and lead 63 back to line 57. With solenoid 65energized, switch arm 66 is raised to its upper position breaking thecircuit through line 62 to motor 23, thus stopping the operation of fan22.

With fan 22 no longer operating, atmospheric pressure quicklyre-establishes itself within casing 26. This atmospheric pressure isthen communicated to chamber 59 via line 52 and the diaphragm them movesto the right to its normal position, opening switch 77. Timer 69 remainsenergized, however, by current flow from line 56 through lead 76, lead84, closed switch 74, lead 85, lead 86, lead 89 and lead 75 to one sideof the timer. Since 8 the other side of timer 69 remains connected toline 57 by way of leads 79 and 63, the timer remains energized for itsset interval so long as switch 74 remains closed.

With switch 71 closed, solenoid 94 of valve 46 is energized as follows:current flows from line 56 through lead 76, lead St), closed switch 71,lead 81, through solenoid 94 and thence through leads 102, 103 and 101back to line 57 to complete the circuit. On the energization of solenoid94, valve core 99 is actuated to its upper position, allowing flowthrough valve 46.

The closing of switch 74 has the effect of energizing solenoid 93 ofvalve 46 as follows: current flows from line 56 through lead 76, lead84, closed switch 74, lead 85, lead 86, lead 109, through solenoid 93,thence back to line 57 by way of lead 101, thus completing the circuit.With solenoid 93 energized, valve core 98 is actuated to its upperposition, allowing flow through valve 40.

As shown particularly in Fig. 3, unevaporated liquid refrigerant withincoil 21, including any refrigerant within line 34 en route to coil 21,then fiows by gravity back through line 39, now open valve 46, into line34 and thence through valve 35, which is normally open during theheating cycle, into heat-exchanger 12 wherein it picks up heat fromwater flowing within tube bundle 14, becoming vaporized thereby. As waspointed out above, valve 46 is open allowing free communication betweenthe two heat-exchangers, equalizing the pressures therein and allowingthe gravity flow. The vaporized refrigerant within the indoorheat-exchanger builds up suflicient pressure to flow through line 36,bypass 45 and open valve 46 into line 32, thence through open valve 33into coil 21. The vaporized refrigerant gives up its heat in coil 21,defrosting the ice formed thereon and becoming condensed thereby withthe liquid refrigerant again flowing by gravity back to indoor coil 21.Water dripping oif coil 21 drops into the pan 26 provided for thispurpose whence it drains away by way of conduit 27 into the sewer.Heaters (not shown) may be added to the pan to melt any frost droppingfrom the coil to keep the water fluid. V

. Upon the completion of the predetermined time cycle as determined bytimer 69, time controlled device 67 is de-energized allowing switch arm70 to drop to its lower position, opening switch 71. Opening switch 71breaks the circuit through solenoid 94, de-energizing the same, allowingvalve core 99 to drop to its lower position, closing flow through valve46. Breaking the circuit through switch 71 de-energizes timer 72.However, since, delayed action timer 72 is set to maintain switch 74closed a predetermined time interval after the de-energization thereof,solenoid 93 remains energized, maintaining valve core 93 in its upperposition and valve 40 open.

With valve 46 closed, the only communication between the heat-exchangersis through line 34. Line 34, however, is full of refrigerant liquid and,therefore does not provide that free communication necessary to allowthe pressure to remain equalized within the indoor and outdoorheat-exchangers. The pressure within the respective heat-exchangers thencorresponds to their temperatures. Since the temperature within indoorheat-exchanger 12 is at a higher temperature than in outdoorheat-exchanger 13, the pressure therein is higher, forcing all theliquid within the indoor heat-exchanger 12 through line 34 and stillopen valve 40 into coil 21. After the predetermined time intervalelapses, delayed action timer 72 allows switch 74 to assume its openposition. Opening of switch 74 breaks the circuit through solenoid coil93, de-energizing the coil, allowing valve core 98 to drop to its lowerposition, closing valve 4! The circuits through solenoids 59 and 65 arealso broken, allowing switch arms 60 and 66 to drop to their lowerpositions closing switches 53 and 64- respectively. With switches 58 and64 closed, motors 11 and 23 are again energized operating the compressor11 andfan 22, and the system again operates on its nor: mal heatingcycle. i

ewage '9 Withythe system 18gb to idefr'o'st 'whenever there is a frostbuild up on coil 21 sufficient to impede the flow of air thereover, itwill be appreciated that the system could "be defrosting any time duringthe day. "It will apparent, of course, that the heat for defrosting thecoil'cornes from .the heat-exchange liquid flowing through tube bunficeforming :in the indoor; coil with .all the'cd'nsequent 'dangers'attached thereto isgreatly minimized. .No thiscellaneous safety controlsare, therefore, required 'to protect the compressor andx'preventfreezing in the indoor "heat-exchanger under normaloperation. It willalso be apparent that LI have-provided in a most expeditious manner forliquid refrigerant return from the indoor to the outdoor heat-exchanger,after the termination of I the defrost cycle.

and 12A with a common water circuit and wherein the water flow throughthe heat-exchangers is in parallel. It is apparent that the water flowthrough the heat-exchangers could be a series flow. The two systems areso interlocked that only one can defrost during any period of timewhereby the other would then provide the heat necessary for defrostingand also would maintain the water temperatures at some reasonable point.

Where such a heat pump system is not in use, or where an additionalsource of heat for defrosting is not available, then I provide thecontrol method as shown in Fig. 4. This consists essentially of a timercontrol set to defrost periodically some time during the night hours sothat even though the water becomes slightly cold, there may be nooccupants in the building to become affected thereby.

A timer device 123 is provided replacing time controlled device 67 andalso,.of course, the diaphragm controlled switch arm 78. Timer device123 essentially comprises a clock of whatever time period is desired,having for example an electrical conducting strip 124 thereon ofsuflicient'length to provide the necessary time for defrosting. Strip124 is placed on the clock in such a manner that the defrost cycle willbegin say at the hour of midnight, or any suitable hour or hours duringthe night. Strip 124 is connected to lead76. A single hour hand 125 isprovided, which is also an electrical conductor and has its one terminalconnected to line 63 by a lead 126. A lead 127 connects lead 82 oftime-oif delay relay 68 with lead 126. It will be seen that lead 81 isnow connected to lead 127.

In operation, when hand 125 in its passage around the clock firstcontacts strip 124,'an electrical circuit is set up through timer device123 by way of lead 76, strip 124, hand 125, lead 126 and lead 63. Thisthen energizes delayed action timer 72 by current flowing from line 56through lead 76, strip 124, hand 125, lead 126,

lead 127 and lead 82 to one side of the timer 72. Theother side of thetimer 72 is connected to line 57 by way of leads 83 and 63. Thenceforththe circuits parallel those of Fig. l. Timer 123 remains energized solong as It will be further seen that I have'provided an apparatus'well'suited in operation and function'for carrying out the statedobjects.

I wish it.jto be understood that my invention is not to "be limited tothe specific constructions and arrangements shown and described, exceptonly insofar as the claims may be so limited, as it will be apparent tothose skilled in the art that changes may be made without departingvfrom the principles of the invention.

What is claimed is: I

1. In a heat pump including a refrigerant compressor, an indoorheat-exchanger and an outdoor heat-exchanger, the combination of meansfor defrosting said outdoor heat-exchanger comprising means for stayingthe operation of said compressor, means establishing flow paths betweensaid heat-exchangers for liquid refrigerant to flow from said outdoortosaid indoor heat-exchanger and evaporated refrigerant to flow from saidindoor to said outdoor heat-exchanger; means for actuating saiddefrosting means; and means for de-actuating saiddeafrosting meanscomprising means for first closing the flow path for evaporatedrefrigerant, and for then closing the flow path for liquid refrigerantand starting said compressor'. I

2. In a heat pump including an indoor heat-exchanger and an outdoorheat-exchanger, the combination of means for defrosting said outdoorheat-exchanger comprising means establishing flow paths between saidheat" 7 exchangers for liquid'refrigerant to flow from said outdoor tosaid indoor heat-exchanger and evaporated refrigerant to flow from saidindoor to said outdoor heatexchanger; means for actuating saiddefrosting means;

' flow rate of the refrigerant en route from said indoor hand 125 moveson strip 124. When hand 125 moves.

off strip 124, the circuit through the timer device is broken,de-energizing coil 94 of valve 46, as aforementioned. After thepredetermined set interval, delayed action timer 72 is de-energizedallowing switch arm 73 to break the circuit through switch 74, all asset out above.

It will be appreciated that the most desirable way of effecting drainageof refrigerant liquid from the outdoor to the indoor heat-exchanger andreturn of refrigerant gas from the indoor to the outdoor heat-exchangerwill be through two separate flow paths. However, I wish it to beunderstood that I contemplate that one flow path may be utilizedprovided it is of sufiicient size to carry both the liquid and gaseousflow. I

It will be seen that I have provided a defrosting arrangement for a heatpump of utmost simplicity characterized by its automatic operation andadmirably suited for carrying out its intended function. The possibility-said flow controlling means for liquid refrigerant to flow through saidcircuit from said outdoor to said indoor heat-exchanger, and meansdefining a flow path for evaporated refrigerant to flow from said indoorto said outdoor heat-exchanger; means for actuating said defrostingmeans; and means for deactuatingsaid defrosting means comprising meansfor first closing said flow path for evaporated refrigerant wherebyevaporating refrigerant will build up to a pressure within said indoorheatexchanger sufficient to force said liquid refrigerant through saidcircuit and bypass means to said outdoor heat-exchanger, and means forthen closing said bypass, and for reactivating said compressor.

4. A defrosting method for a heat pump having a com pressor, an indoorheat-exchanger, and an outdoor heatexchanger comprising the steps ofdeactuating the compressor, providing direct communication between saidheat-exchangers for equalizing the pressures therebe} tween, flowingliquid refrigerant from said outdoor to said indoor heat-exchanger,passing the liquid refrigerant within the indoor heabexchanger inheat-exchange relation with a heat-exchange liquid therein to absorbheat therefrom and become vaporized, flowing the vaporized refrigerantback to the outdoor heat-exchanger to give up its heat therein fordefrosting purposes, and terminating the defrosting operation bypartially closing communication between the two heat-exchangers, wherebya normally higher pressure in the indoor heat-exchanger Will reestablishitself, said higher pressure then forcing liquid refrigerant from theindoor back to the outdoor heat-exchanger, and reactuating saidcompressor.

UNITED STATES PATENTS Gibson Nov. 1,

Crago Jan. 10, 1939 MeCloy June 13,1944 Leeson Nov. 18, 1947 SchordineJuly 19, 1955 Ellenberger Dec. 27, 1955 Raney May 8, 1956 Parcaro June5, 1956 Cain Oct. 30, 1956 Fifield Aug. 6, 1957 UNITED STATES PATENTOFFICE; CERTIFICATE OF CORRECTION Patent No, 2 928 255 March 15 1960James R. Harnish It is hereby certified that error appears inthe-printed specification of the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 5 lines 29 and 30 after "arm 73 for" strike out o pen:"m.g oropening or".

Signed and sealed this 23rd day of August 1960,

( SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Commissioner of Patents AttestingOfficer

